1. Field of the Invention
The invention is concerned with latex compositions and with methods for the preparation of such latexes. The polymer particles comprising the latex have stabilizing, pH independent ions chemically bound at or near the surface of the particles.
2. Description of the Prior Art
Latexes require some means for providing colloidal stabilization in aqueous media. The usual colloidal stabilization is provided for surfactants which usually are anionic or cationic but may be non-ionic, especially in mixtures with anionic or cationic surfactants. Even though they contribute to the required colloidal stability, the surfactants can interfere with coating performance of the latexes even though the amount is limited and less than the desired stability is obtained. Another method is to copolymerize with non-ionic monomers a small proportion of an ionic monomer to prepare a stable latex with little or no conventional surfactant as described in U.S. Pat. No. 3,637,432. Such processes, however, require special combinations of monomers and special polymerization techniques. Although such processes produce latexes having little or no surfactants, varying amounts of water-soluble products are made during carrying out of the process and remain in the product.
U.S. Pat. No. 3,236,820 describes the reaction of anionic latexes of polymers of vinylbenzyl chloride with sulfides to produce water-soluble cationic polymers. By starting with an anionic emulsion, the conversion of the polymerized vinylbenzyl chloride units on the particle to cationic groups causes destabllization of the latex. If the proportion of vinylbenzyl chloride units in the polymer is not high enough to render the polymer water-soluble in the converted form, the latex will coagulate.
Some of the latexes suitable for the practice of this invention are described and claimed in Applicant's copending application Ser. No. 569,724, filed Apr. 21, 1975, now U.S. Pat. No. 4,017,442.